Cross-linking is a process in which polymer chains are associated through chemical bonds. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behaviour. In this study there was found that ionizing beta radiation increased the nano-mechanical properties of polyamide 11 (PA11). The measurement results indicated that ionizing beta radiation (66kGy, 132kGy and 198kGy) was a very effective tool for improvement of indentation hardness, indentation modulus, indentation creep and deformation works of studied polymers. The best results were achieved by irradiation at doses of 132 kGy (increase about 40%) by which the highest nano-mechanical properties of PA11 were achieved.